Problem: $ D = \left[\begin{array}{rrr}0 & 0 & 2 \\ 1 & 1 & 1 \\ 2 & 0 & 1\end{array}\right]$ What is $ D^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}-\frac{1}{4} & 0 & \frac{1}{2} \\ -\frac{1}{4} & 1 & -\frac{1}{2} \\ \frac{1}{2} & 0 & 0\end{array}\right]$